Many technological advances have resulted in the provisioning and delivery of telephony services over packet networks. However, congested network conditions introduce a new problem when providing telephony services over packet networks. In past circuit switched telephony networks, the circuit network was able to proactively handle congestion in switches through call blocking or call gapping. However, packet networks utilized for telephony service are not equipped with such mechanisms and are only able to operate at a certain capacity and serve a limited number of call requests. Additionally, some providers of telephony services over packet networks utilize a call control system to assist in setting up and tearing down calls, and the call control system may also become congested.
The limit on the capacity of the call control system may be due to the number of processors, protocol stacks, or queues in the call control system, or other reasons. During a mass call event, the number of incoming calls may well exceed the capacity of the call control system or the packet network, which results in the call control system or network entering a state of congestion. Unfortunately, when congestion occurs in the network or call control system, a user attempting to place a high priority call, such as a request for an emergency service, may not be connected to the called party.